There is a system of monitoring an in-vehicle component based on data acquired from a vehicle; wherein the system finds in advance mileage (replacement reference mileage) of the vehicle, which is a measure for component replacement time, compares this replacement reference mileage and actual mileage, and notifies the user that it is the component replacement time when the actual mileage reaches the replacement reference mileage.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2003-137079    [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2003-346010